1. Field of the Invention
The present invention relates to a method, system, and program for generating and indicating incremental backup copies from virtual copies of a data set
2. Description of the Related Art
In many systems, data on one storage system may be copied to the same or another storage system so that access to data volumes can be provided from two different storage systems. A point-in-time copy involves physically copying all the data from source volumes to target volumes so that the target volume has a copy of the data as of a point-in-time. A point-in-time copy can also be made by logically making a copy of the data and then only copying data over when necessary, in effect deferring the physical copying. This virtual copy operation is performed to minimize the time during which the target and source volumes are inaccessible.
With a virtual copy operation, the copy services performing the virtual copy create metadata and data structures providing a logical representation of source data as a point in time. The virtual copy is completed almost instantly, in the time taken to create the metadata and data structures and is completed without any physical copying of the data. If the source data subject to a virtual copy is updated following the creation of the virtual copy, then the original data in the source data is copied to a storage pool maintained for the virtual copy before the data is updated. In this way, the source data as of the point-in-time of the virtual copy may be reconstructed from the unchanged source data and the original data that was overwritten in the source data maintained in the virtual copy storage pool. Examples of a virtual copy operation include the International Business Machines Corporation's® Snapshot copy and FlashCopy® operations. (FlashCopy and International Business Machines are registered trademarks of International Business Machines Corp. in the United States and other countries).
A user or application may also use a database or other program to create incremental backups of source data. An incremental backup is performed with respect to a base data set, comprising a full copy of a data set at an initial point-in-time, and includes data that has changed since the full copy of the data set or a most recently created incremental backup set. In this way, the incremental backup set includes only data that has changed since the last created full or incremental backup set.
There is a need in the art to utilize both virtual copy and incremental backup operations in a backup environment.